College Answer

TEN is condition involving rapid progression of erythems and extensive (usually > 30% epidermis involved) epidermal necrolysis. It overlaps with the Stevens-Johnson syndrome, and has a high mortality rate (up to 44%!). Early dermatological consultation is important. Diagnostic features include:

Most cases are drug induced, few are idiosyncratic. The commenest drugs to be implicated are: sulphonamides antibiotics, aminopenicillins, quinolones, cephalosporins, carbemazepine, phenobarbital, phenytoin, valproic acid, NSAIDs, allopurinol and corticosteroids! TEN is more common in patients with SLE and HIV.

Discussion

Stevens-Johnson Syndrome and TEN are considered diseases of the same spectrum. SJS is the less severe classification of the same disease: only ~ 10% of the skin surface is sloughed. TEN, on the other hand, is a condition of over 30% slough. In the 10-30% patients, the two conditions overlap. This condition had come up again thirteen years later, in Question 28 from the second paper of 2018 which asked for a lot more detail about TEN, and which was actually done much better (pass rate was 58.2%).

Thus, the diagnostic features:

History of exposure to a new drug

1-3 weeks of waiting

Fever and flu-like symptoms for 1-3 days before skin eruption

Skin eruption: poorly defined macules with purpuric centres

Then, blisters and epidermal detachment

Symmetrical, primarily over face and upper trunk

Complications similar to burns

Mucosal involvement in 90%

BOOP and respiratory mucosal sloughing can also occur

Drugs which are known to cause TEN:

phenytoin

NSAIDs

Penicillins

Quinolones

Carbamazepine

Valproate

Allopurinol

Fluconazole

Sulfonamides

Barbiturates

Non-drug causes of TEN:

Mycoplasma pneumoniae(next most common cause)

HIV

HSV

Influenza virus

Coxsackie

Mumps

Malignancy (though this is usually listed as a risk factor or association)